[snapshot] introduce SnapshotCreator API.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 255ac0e90cf1b41480ab7d9feb3d66bb7d8a7857..4cb6cb54d82d322efe33986ef9ca8db78ad00837 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -6492,6 +6492,46 @@ class V8_EXPORT V8 {
                                             const char* warmup_source);
 
   /**
+   * Helper class to create a snapshot data blob.
+   */
+  class SnapshotCreator {

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

I'd not make this a subclass of V8 but a top-level class

[Yang, 2016/06/08 13:30:29]

Done.

+   public:
+    enum FunctionCodeHandling { CLEAR_FUNCTION_CODE, KEEP_FUNCTION_CODE };

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

what about using an enum class { kClear, kKeep}

[Yang, 2016/06/08 13:30:29]

Done.

+
+    /**
+     * Create an enter an isolate, which is correctly set up for serialization.
+     * The isolate is either created from scratch or from an existing snapshot.
+     * The caller keeps ownership of the argument snapshot.
+     */
+    explicit SnapshotCreator(StartupData* existing_blob = nullptr);

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

can you explain why the existing snapshot is needed?

[Yang, 2016/06/08 13:30:29]

As discussed, this is for creating warmed up snapshots.

+
+    ~SnapshotCreator();
+
+    /**
+     * \returns the isolate prepared by the snapshot creator.
+     */
+    Isolate* GetIsolate();
+
+    /**
+     * Add a context to be included in the snapshot blob.
+     */
+    void AddContext(Local<Context> context);
+
+    /**
+     * Created a snapshot data blob.
+     * \param function_code_handling whether to include compiled function code
+     *        in the snapshot.
+     * \returns { NULL, 0 } on failure, and a startup snapshot on success. The

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

nullptr? 

[Yang, 2016/06/08 13:30:29]

Done.

+     *        caller acquires ownership of the data array in the return value.
+     */
+    StartupData CreateBlob(
+        FunctionCodeHandling function_code_handling = CLEAR_FUNCTION_CODE);

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

I don't think the default arg is needed

[Yang, 2016/06/08 13:30:29]

Done.

+
+   private:
+    void* data_;
+  };

[jochen (gone - plz use gerrit), 2016/06/08 13:06:48]

do we have some DISALLOW_COPY_AND_ASSING in the API?

[Yang, 2016/06/08 13:30:29]

We don't have it as a macro, but override the copy constructor and = operator in
some places.

I could also use DISALLOW_COPY_AND_ASSIGN on the ArrayBufferAllocator member to
achieve the same effect...

+
+  /**
    * Adds a message listener.
    *
    * The same message listener can be added more than once and in that